While Unlikely To Be Carcinogenic, The Herbicide Glyphosate Is A Symptom Of A Deep Social Pathology

On both sides of the Atlantic a battle is raging between starkly opposed views of what science tells us about risks to our health emanating from our surroundings, including our food, water, and the wider environment.

This battle often pits advocates, nongovernmental organizations (NGOs), politicians, and partisan scientists, who have little ability or inclination to evaluate the evidence on its merits, against scientists and regulators who confine themselves to evaluating the evidence but are typically characterized as corrupt apologists for industry. Unfortunately, confining oneself to the scientific issues simply does not have the same impact in the public arena as holding up the specter of an imminent threat to our well-being, and the less sensationalist party in this lop-sided contest is often left to tear its hair out in frustration.

At the moment, a major focus in this battle is glyphosate, the most widely used herbicide (i.e., weed killer) in the United States. Glyphosate is the active ingredient in Monsanto’s Roundup, and a number of major crops have been genetically engineered to be resistant to Roundup.

In response to a new report alleging a cancer risk from trace residues of glyphosate, which has sparked renewed pressure from anti-pesticide NGOs, this past June the European Union voted against re-registering glyphosate for agricultural use in Europe but agreed to an 18-month extension of the license. In the U.S. glyphosate is also at the center of a tangled regulatory battle.

Glyphosate and compounds containing the chemical, like Roundup, have been reviewed for health effects by a number of health agencies, including the European Food Safety Authority (EFSA), the Food and Agricultural Organization (FAO), Germany’s Institute for Environment and Human Security (BfR), and the U.S. Environmental Protection Agency (EPA). These agencies have concluded that glyphosate is unlikely to pose a carcinogenic risk to humans.

However, in March 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as a “probable carcinogen.” IARC stated that its determination was based on “clear evidence of cancer in experimental animals, limited evidence for cancer for humans from real-world exposures, of exposed farmers, and also strong evidence that it can damage the genes and other toxicological studies."

A number of other recent determinations by IARC have perplexed both scientists and the public, most famously those pertaining to coffee, red meat, and cell phones. It has become clear that IARC takes a very different approach to assessing carcinogens than most other agencies. Rather than taking into account real-world exposure to an agent and what is known about its ability to cause cancer at various exposure levels – risk assessment – IARC’s assessment takes into account the potential to cause cancer under theoretical conditions – hazard assessment. This approach is considered outmoded and unscientific by many scientists and regulatory agencies (accepted manuscript Boobis A, Cohen, S, Dellarco V, et al. "Classification schemes for carcinogenicity based on hazard-identification have become outmoded and serve neither science nor society," Regulatory Toxicology and Pharmacology, Oct. 2016).

Under IARC’s “hazard assessment,” weak and difficult-to-interpret findings can be given undue weight and can take precedence over other stronger types of evidence that do not point to a threat, such as that from epidemiologic studies in humans and whole animal studies.